HOUSTON, March 21 (Reuters) - Venezuela's state-run oil company PDVSA has accumulated $21. The internal disclosure of the enormous amount of unpaid sales - about 84% of PDVSA's total value of invoiced shipments - reveals for the first time the depths of revenue losses due to the withdrawal of established oil company buyers since 2020. EXECUTIVES ARRESTEDPDVSA's former vice president of supply and trade, Antonio Perez Suarez, and about 20 executives who worked for him have been arrested, according to people familiar with the matter